So, I did a phone reset. Unfortunately the issue is still present!
Sometimes when I press the power button to unlock the phone the screen is lit, but stays blank i.e. no lockscreen wallpaper, no nothing. The same happens sometimes when I get a phone call - the phone rings and vibrates, the screen is lit but stays blank.
When this happens I have to press the power button to put the phone into sleep mode and press it again to wake it up.
What I found is, when the issue occurs the screen is actually responsive. For example I can slid up and unlock the phone then I hear the unlock "pop" sound. It's just that nothing is drawn on it!
I was wondering if anyone else experienced the same behavior and found a resolution. Also I am not sure if this is a software or a hardware problem. If I could confirm it was a hardware problem I would call LG and have the phone repaired or replaced.